Pneumatically switchable type fluid-filled engine mount

ABSTRACT

A fluid-filled engine mount, including: an elastic body connecting a first and a second mounting member; a pressure receiving chamber partially defined by the rubber elastic body; an equilibrium chamber partially defined by a flexible layer, a first orifice passage connecting between the pressure receiving and equilibrium chambers and tuned to a low frequency range, a second orifice passage connecting the both chambers and tuned to a medium frequency range; a valve member for opening/closing the second orifice passage and operated by a pneumatic actuator; a movable partition member including a rigid center movable plate portion and a readily deformable outer peripheral rubber film portion supported fluid-tightly by the second mount portion; and an intermediate equilibrium chamber formed opposing to the pressure receiving chamber with the movable partition member interposed therebetween.

INCORPORATED BY REFERENCE

The disclosure of Japanese Patent Application No. 2004-153868 filed onMay 24, 2004 and No. 2004-160332 filed on May 28, 2004, each includingthe specification, drawings and abstract are incorporated herein byreference in its entirety,

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an engine mount for vibration-isolatingsupport of a power unit on a body of an automobile, and moreparticularly to a fluid-filled engine mount of improved construction,that utilizes the flow action of non-compressible fluid sealed in itsinterior to produce effective vibration damping action against vibrationof multiple, wide frequency ranges, such as engine shake and idlingvibration.

2. Description of the Related Art

There are known in the art, as an engine mount for use in automotivevehicles, an engine mount of fluid-filled design having a first mountfixture and a second mount fixture for respective attachment to eitherthe power unit or the vehicle body, a rubber, elastic body elasticallyconnecting the fixtures, a pressure receiving chamber whose wall ispartially formed by the rubber elastic body, and an equilibrium chamberwhose wall is partially formed by a readily deformable flexible layer. Anon-compressible fluid is sealed within the pressure receiving chamberand equilibrium chamber, and an orifice passage is provided for acommunication between the two chambers.

Typically, an automotive engine mount is required to meet a variety ofvibration to be damped whose frequencies differ depending on drivingconditions. However, vibration-damping action based on flow action offluid flowing through the orifice passage is limited to a relativelynarrow frequency band to which the orifice passage has been pre-tuned.

The present assignee has been proposed in JP-A-8-270718, a pneumaticallyswitchable type, fluid filled engine mount including: a first orificepassage tuned to the frequency of a first vibration to be damped; asecond orifice passage tuned to the frequency of another vibration to bedamped in a higher frequency band than the tuning frequency of the firstorifice passage; a valve member for opening/closing the second orificepassage; and a pneumatic actuator that utilizes air pressure exertedfrom the outside to drive the valve member. In this engine mount, thevalve member is driven so that the second orifice passage is placed inthe closed state by means of atmospheric pressure exerted on thepneumatic actuator from the outside, or so that the second orificepassage is placed in the open state by means of negative pressureexerted from the outside, whereby the first orifice passage and secondorifice passage are made to function selectively depending on thevibration to be damped, thereby producing the desired vibration dampingaction.

In recent years, an even higher level of vibration damping performancehas come to be required, and in some instances the engine mount taughtin JP-A-8-270718 is not sufficient to affords the required level ofvibration damping performance. One required characteristic is dampingability against high frequency vibration such as running booming noise,which can be a problem during driving. Another required characteristicis damping ability against low frequency vibration such as engine shake,which can be a problem during driving. With regard to this latter lowfrequency vibration, damping ability against two types of vibration,namely low frequency; large amplitude vibration which is a problem whendriving over speed bumps or the like, and low frequency, small amplitudevibration which is a problem during normal driving.

To coop with the first instance the required characteristic of dampingability against high frequency vibration, the present applicant has beenproposed, as taught in JP-U-2-25749, to dispose a rigid movable plate inthe partition wall that divides the pressure receiving chamber and theequilibrium chamber so that the plate is displaceable over a very smalldistance, whereby when high frequency vibration above the tuningfrequency band of the first orifice passage and second orifice passageis input, pressure fluctuations in the pressure receiving chamber areabsorbed by a very small level of displacement of the movable plate,creating lower dynamic spring.

However, when such a movable plate is employed, there is a risk thatpressure fluctuations occurring in the pressure receiving chamber willbe absorbed by displacement of the movable plate, even at times of inputof small amplitude vibration in the low frequency range. This makes itdifficult to ensure adequate fluid flow level through the first orificepassage tuned to the low frequency range, resulting in the difficulty inachieving sufficient attenuating action on low frequency, smallamplitude vibration. Additionally, the rigid movable plate needs a gapon the outer peripheral side of the movable plate in order to permitslight displacement thereof, likely permitting a leak of fluid pressurefrom the pressure-receiving chamber to the equilibrium chamber throughthe gap. As a result, pressure fluctuations occurring in the pressurereceiving chamber during input of low frequency, small amplitudevibration or medium frequency, medium amplitude vibration can leak,making it difficult to assure adequate fluid flow level through thefirst and second orifice passages, with the resultant problem of adecline in damping ability against the low amplitude component of engineshake and the medium amplitude component of idling vibration.

With the foregoing in view, the present application has also proposed,as taught in JP-A-9-310732, to dispose a movable film consisting of thinrubber film in place of the rigid movable plate, whereby liquid pressureabsorbing action based on elastic deformation of the movable filmprovides lower dynamic damping of high frequency vibration above thetuning frequency range of the second orifice passage.

However, it was found that, just as with the movable plate mentionedearlier, when such a movable film was employed, there was a risk thatelastic deformation of the movable film would absorb pressurefluctuations in the pressure receiving chamber, including low frequency,small amplitude vibration and medium frequency, medium amplitudevibration. This makes it difficult to provide sufficient damping actionagainst engine shake and idling vibration.

To address this problem, the applicant has further proposed, as taughtin JP-A-5-118375, to provide a working air chamber to the opposite sideof the movable film from the pressure receiving chamber, whereby inassociation with negative pressure exerted on the working air chamberfrom the outside, the movable film is made to undergo constrainingdeformation, limiting the extent of elastic deformation thereof. Namely,by ensuring a sufficiently high level of fluid flow through the firstorifice passage and second orifice passage during input of engine shakeor idling vibration, by means of limiting the extent of elasticdeformation of the movable film to suppress absorption of pressurefluctuations in the pressure receiving chamber, damping action of engineshake or idling vibration can be advantageously realized.

However, in the fluid-fluid engine mount disclosed in JP-A-5-118375,when limiting the extent of elastic deformation of the movable film, inconsideration of phase difference, movable film free length, working airchamber size etc., negative pressure is exerted on the working airchamber, and the movable film undergoes a high level of undergoconstraining deformation. This makes the mount control system andoverall construction complicated. Thus, with the engine mount inquestion there are appreciable disadvantages in terms of productionefficiency and production costs, another inherent problem is thedifficult of installation in an automobile.

Further, the present applicant has made another proposal, while focusingon the fact that vibration which poses a problem in the high frequencyrange typically has small amplitude. Namely, as taught, for example, inJP-A-2000-310274 and JP-A-2001-200884, the present assignee has proposedto dispose a slightly displaceable removable plate extending at agenerally right angle to the direction of opposition of the pressurereceiving chamber and the equilibrium chamber with respect to apartition member, whereby pressure fluctuations produced in the pressurereceiving chamber by input of vibration in the high-frequency band abovethe tuning frequency band of the first orifice passage and secondorifice passage can be absorbed by minute displacement of the movableplate, producing a low dynamic spring rate.

Where this kind of movable plate was employed, however, there was a riskthat pressure fluctuations produced in the pressure receiving chamberwould be absorbed by displacement of the movable plate, even duringinput of vibration in the low- to medium-frequency range,

Specifically, vibration in the medium-frequency range, such as idling,typically has small amplitude of ±0.1-0.25 mm. As regards vibration inthe low-frequency range, such as engine shake that is a problem duringdriving, there is now required effective vibration damping not only oflarge amplitude on the order of ±1.0 mm such as occurs when driving overspeed bumps or the like, which has been considered a problem for sometime, but also of small amplitude on the order of ±0.1 mm occurringduring normal driving. Thus, as regards vibration of the low- tomedium-frequency range having relatively small amplitude, if pressurefluctuations in the pressure receiving chamber are absorbed throughsmall displacement of the movable plate, there is a risk that that fluidflow level through the first orifice passage or second orifice passagewill be insufficient to afford adequate vibration damping action.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a pneumaticallycontrolled, fluid filled engine mount of simple constructionadvantageously affording damping action against multiple, wide frequencyranges, as well has having improved case of installation in anautomobile.

It is another object of the present invention to provide a pneumaticallycontrolled, fluid filled engine mount of novel construction whichreduces or avoids markedly high dynamic spring rate in the highfrequency range while adequately assuring vibration damping effect by afirst orifice passage tuned to the low-frequency range and a secondpassage tuned to the medium-frequency range, and which exhibitseffective vibration damping action against vibration of multiple andbroad frequency ranges.

The above and/or optional objects of this invention may be attainedaccording to at least one of the following modes of the invention. Thefollowing modes and/or elements employed in each mode of the inventionmay be adopted at any possible optional combinations. It is to beunderstood that the principle of the invention is not limited to thesemodes of the invention and combinations of the technical features, butmay otherwise be recognized based on the teachings of the presentinvention disclosed in the entire specification and drawings or that maybe recognized by those skilled in the art in the light of the presentdisclosure in its entirety.

The principle of the present invention provides a pneumaticallyswitchable type fluid-filled engine mount, comprising: (a) a firstmounting member attachable to one of a power unit side member and avehicle body side member; (b) a second mounting member attachable to another of the power unit side member and the vehicle body side member;(c) a rubber elastic body elastically connecting the first mountingmember and the second mounting member; (d) a pressure receiving chamberpartially defined by the rubber elastic body, filled with anon-compressible fluid, and subjected to input of vibration; (e) anequilibrium chamber partially defined by a flexible layer for readilypermitting change in volume thereof, and filled with thenon-compressible fluid; (f) a first orifice passage for fluidcommunication between the pressure receiving chamber and the equilibriumchamber, tuned to a low frequency range generally corresponding toengine shake; (g) a second orifice passage for fluid communicationbetween the pressure receiving chamber and the equilibrium chamber,tuned to a medium frequency range generally corresponding to idlingvibration; (h) a valve member for opening/closing the second orificepassage; (i) a pneumatic actuator operated by air pressure from theoutside, for driving the valve member; (j) a movable partition memberwhose center portion constitutes a rigid center movable plate portionand whose outer peripheral portion constitutes a readily deformableouter peripheral rubber film portion, disposed so that an outerperipheral edge of the outer peripheral rubber film portion is supportedfluid-tightly by the second mount portion, permitting displacement anddeformation in the center movable plate portion and the outer peripheralrubber film portion, the movable partition member defining another partof the pressure receiving chamber; and (k) an intermediate equilibriumchamber formed on an opposite side of the movable partition member fromthe pressure receiving chamber with the movable partition memberinterposed between the intermediate equilibrium chamber and the pressurereceiving chamber.

In the fluid filled engine mount constructed in accordance with thepresent invention, although the center portion of the movable partitionmember tends to readily deform in association with vibration input tothe pressure receiving chamber owing to its location away from the outerperipheral edge supported by the second mounting member, by means ofdisposing a rigid center movable plate portion in the center portion,the extent of displacement of the movable partition member is held downappropriately. Additionally, by making the center portion of the movablepartition member rigid, excessive deformation can be suppressed evenwhere the movable partition member is large. Thus, during input of low-to medium-frequency vibration, for which it is desirable for effectivepressure fluctuation to be produced in the pressure receiving chamber,liquid pressure absorption by the movable partition member can be heldin check despite the small amplitude of input vibration down to acertain point, so that pressure fluctuations are effectively produced inthe pressure receiving chamber.

Additionally, by disposing a readily deforming peripheral movable rubberfilm portion in the outer peripheral portion of the center movable plateportion, particularly when vibration in the high-frequency band is inputto the pressure receiving chamber, the movable partition member,principally on the basis of deformation of the peripheral movable rubberfilm portion, undergoes displacement and deformation in response to thehigh-frequency vibration, so that pressure fluctuations in the pressurereceiving chamber are advantageously suppressed.

In the fluid filled engine mount constructed in accordance with thepresent invention, during input of low frequency, large amplitudevibration such as engine shake produced by driving over a speed bump orstep, there is prevented an associated absorption of liquid pressure bymeans of displacement and deformation of the movable partition membercomposed of a center movable plate portion and an outer peripheralrubber film portion. This produces effective pressure fluctuationswithin the pressure-receiving chamber, thereby enabling relativepressure fluctuations to be created between the pressure receivingchamber and the equilibrium chamber. Thus, the second orifice passage ismaintained in the closed state by the valve member, ensuring an adequatelevel of fluid flow through the first orifice passage, so as to achievea high level of attenuating effect based on flow action (e.g. resonanceaction) of the fluid induced to flow through the first orifice passage,so that excellent vibration damping ability is exhibited.

When low frequency, small amplitude vibration corresponding to engineshake etc. produced, during normal driving, for example, by means of thefact that the outer peripheral rubber film portion assures a fluid tightseal at the outer peripheral side of the center movable plate portion,and the fact that the center movable plate portion is rigid so as tosuppress the extent of deformation of the movable partition member,absorption of pressure of the pressure receiving chamber by the movablepartition member is suppressed, whereby sufficiently effective pressurefluctuations are produced in the pressure receiving chamber. Thus, as inthe case of low frequency, large amplitude vibration mentionedpreviously, as long as the second orifice passage is in the closed stateby the valve member, an adequate level of fluid flow through the firstorifice passage is effectively assured, and a high level of attenuatingeffect based on flow action (e.g. resonance action) of the fluid inducedto flow through the first orifice passage to achieved, so that excellentvibration damping ability is exhibited.

Further, during input of high frequency, small amplitude vibrationcorresponding for example to booming noise produced during driving,since pressure fluctuations in the pressure receiving chamber areextremely small, pressure fluctuations in the pressure receiving chambercan be reduced based on displacement and deformation of the movablepartition member. In particular, by having the center movable plateportion of the movable partition member formed in the center portion,effective surface area on the part of the center movable plate portion19 effectively assured. Additionally, since outer peripheral rubber filmportion which provides fluid-tight support at the outer peripheral edgeof the movable partition member is readily deformable, the member canundergo displacement and deformation in association with high frequencyvibration in the pressure receiving chamber, effectively suppressingpressure fluctuations of the pressure receiving chamber. Thus, whenvibration in the high frequency band is input, even if the first andsecond orifice passages are in a substantially closed state, markedpressure fluctuations of the pressure receiving chamber can be avoidedby means of the movable partition member, and by means of effectivevibration isolating action based on low dynamic spring characteristics,excellent vibration damping or isolating action may be achieved. Forinstance, when a natural frequency of the movable partition member istuned to a high frequency band corresponding to a running booming noise,the movable partition member more likely undergoes displacement ordeformation on the basis of its resonance action, further effectivelypreventing pressure fluctuation induced in the pressure receivingchamber.

Additionally, during input of medium frequency, medium amplitudevibration corresponding for example to idling vibration etc. occurringwith the vehicle at a stop, absorption of pressure of the pressurereceiving chamber by the movable partition member is a concern. However,since the extent of deformation of the movable partition member issuppressed on the basis of the rigid center movable plate portiondisposed in the center portion of the movable partition member, andsince, due to the fact that the outer peripheral rubber film portion isprovided on the outer peripheral side of the center movable plateportion ensuring a fluid tight seal of the pressure receiving chamber,pressure leakage from the pressure receiving chamber to the equilibriumchamber is avoided. Thus, adequate pressure fluctuations can be createdin the pressure-receiving chamber. With the second orifice passage beingplaced in the open state by operation of the pneumatic actuator, anadequate level of fluid flow through the second orifice passage can beadequately assured, whereby a high level of attenuating effect based onflow action (e.g. resonance action) of fluid induced to flow through thesecond orifice passage is achieved, so that excellent vibration dampingability is exhibited. With the second orifice passage in the open state,the first orifice passage is in the open state as well. However, duringinput of medium frequency vibration in a frequency range above of thetuning frequency of the first orifice passage, the first orifice passagebecoming substantially closed due to anti-resonant action of fluidthrough the first orifice passage, the level of fluid flow through thesecond orifice passage will be effectively assured.

That is, the fluid filled engine mount of the present invention employsthe movable partition member comprising the center movable plate portionand the outer peripheral rubber firm portion. With this arrangement, inresponse to input of high frequency, very small amplitude vibration ofthe kind described previously for example, liquid pressure absorbingaction on the part of the movable partition member can be made tofunction effectively. Thus, high dynamic spring on the part of thepressure receiving chamber can be suppressed to achieve excellentvibration isolating effect. While in response to low frequency, smallamplitude vibration and medium frequency, small medium vibration forexample, the extent of deformation of the movable partition member issuppressed and fluid tightness of the pressure receiving chamber isassured, whereby effective pressure fluctuations are produced in thepressure receiving chamber. Thus, by selectively switching the secondorifice passage between the closed and open states, vibrationattenuating action based of fluid flow action through the orificepassages can be effectively achieved.

Thus, in this embodiment, by means of employing a movable partitionmember of the sort described above, the desired damping action ofvibration of multiple, wide frequency ranges can be achieved by means ofrelatively simple construction, to effectively realize an engine mountwith excellent production efficiency and cost performance.

Additionally, in the engine mount of the present invention, since thereis no express need for a construction to control the level ofdisplacement and deformation of the movable partition member dependingon the vibration frequency being damped, the control system can besimplified, the process of installation in an automobile can be madeeasier, and operating costs pertaining to the mount can beadvantageously reduced.

According to the first advantageous form of the invention, theintermediate equilibrium chamber comprises an aft chamber open to anatmosphere. With this arrangement, the intermediate chamber can beeasily formed with simple construction.

According to the second advantageous form of the invention, the firstmounting member is disposed at and spaced apart from a first axial openend of the second mounting member of cylindrical shape, with the firstmounting member and the second mounting member being connected by therubber elastic body to thereby fluid-tightly close the first axial openend of the second mounting member, and an other open end of the secondmounting member is covered fluid-tightly by the flexible layer, while apartition member is disposed between the rubber elastic body and theflexible layer and supported by the second mounting member so that thepressure receiving chamber and equilibrium chamber are formed to eitherside of the partition member; wherein the movable partition member isdisposed in the partition member on a side facing the pressure receivingchamber, and the intermediate equilibrium chamber is formed on a backside of the movable partition member remote from the pressure receivingchamber in the partition member, while an air passage is formedextending from the air chamber to an outer circumferential surface ofthe second mounting member through the partition member and the secondmounting member; wherein the first orifice passage is formed so as toextend along an outer peripheral portion of the partition member in ancircumferential direction, and the second orifice passage is formed soas to extend with a predetermined length in an axial direction at anouter peripheral side of the movable partition member in the partitionmember, and extend radially inwardly through an inner portion of thepartition member, the second orifice passage being open to thepressure-receiving chamber through a fist opening formed at an outerperipheral side of the movable partition member in the partition memberand being open to the equilibrium chamber through a second openingformed at a central portion of the partition member; and wherein theflexible layer is superimposed onto the second opening of the secondorifice passage to constitute the valve member, the valve member beingdriven by the actuator to carry out opening/closing control of thesecond orifice passage by alternately opening and closing the secondopening of the second orifice passage, and a second opening peripheralportion that extends outwardly in an axis-perpendicular direction fromthe second opening of the second orifice passage has a dilated shape ofgradually increasing width dimension in the circumferential directiongoing outwardly in the axis-perpendicular direction.

In this embodiment, the first and second orifice passages are formedutilizing the partition member which divides the pressure receivingchamber and the equilibrium chamber, and the movable partition memberand air chamber are disposed in the partition member. Thus, the membersae functionally disposed, thereby realizing overall compactconstruction.

With the fluid filled engine mount of this advantageous form, theportion that extends outwardly in the axis-perpendicular direction fromthe second opening of the second orifice passage on the equilibriumchamber side is imparted with a dilated shape of gradually increasingwidth dimension in the circumferential direction going outwardly in theaxis-perpendicular direction, whereby it is possible to maintain a gooddegree of freedom in design of the first orifice passage in thepartition member, the air chamber, the movable partition member etc.,while making it possible to ensure large capacity of the second orificepassage. Additionally, when vibration damping characteristics givingwise to effective pressure fluctuations are required of the pressurereceiving chamber, even in instances where pressure absorption of thepressure receiving chamber is produced at a predetermined level by meansof the movable partition member, since the second orifice passage haslarge capacity, a sufficiently large flow of fluid caused to flowthrough the second orifice passage is assured. Thus, the expectedvibration damping effect (high damping effect) is obtained on the basisof flow action of fluid through the second orifice passage.

According to the third advantageous form of the invention, theintermediate equilibrium chamber is formed integrally with theequilibrium chamber so that the center movable plate portion and theperipheral movable rubber film portion undergo displacement anddeformation on the basis of a pressure difference between the pressurereceiving chamber formed on one side thereof and the equilibrium chamberformed on an other side thereof so as to absorb, by means of thedisplacement and deformation, pressure fluctuation in the pressurereceiving chamber during input of vibration in a high frequency bandcorresponding to drive booming noise.

According to the fourth advantageous form of the invention, a portion ofthe equilibrium chamber is constricted to form a fluid passage, and thedisplacement and deformation of the movable partition member based on apressure difference between the pressure receiving chamber and theequilibrium chamber, exerted on either face of the movable partitionmember permits a substantial fluid flow through the fluid passage.

This advantageous form ensures a large flow level of fluid induced toflow through the fluid passage on the basis of displacement anddeformation of the movable partition member, whereby vibration dampingaction based on flow action, e.g. resonance action, of fluid through thefluid passage may be, advantageously achieved. Thus, by tuning the fluidpassage to a particular frequency range of vibration to be tamped,vibration damping effect is exhibited advantageously over a wide range.Further, in this embodiment, since a portion of the equilibrium chamberis utilized in forming the fluid passage, sufficient passage length canbe advantageously assured, without any accompanying increase in size ofthe mount as a whole.

According to the fifth advantageous form of the invention, the firstmounting member is disposed at and spaced apart from a first axial openand of the second mounting member of cylindrical shape, with the firstmounting member and the second mounting member being connected by therubber elastic body to thereby fluid-tightly close the first axial openend of the second mounting member, and an other open end of the secondmounting member is covered fluid-tightly by the flexible layer, while apartition member is disposed between the rubber elastic body and theflexible layer and supported by the second mounting member so that thepressure receiving chamber and equilibrium chamber are formed to eitherside of the partition member; wherein the movable partition member isdisplaceably and deformably disposed so as to extend at a generallyright angle to the direction of opposition of the pressure receivingchamber and the equilibrium chamber in the partition wall member; andwherein the first orifice passage is formed so as to extend along anouter peripheral portion of the partition member in an circumferentialdirection, and the second orifice passage is formed so as to extend witha predetermined length in an axial direction at an outer peripheral sideof the movable partition member in the partition member, and extendradially inwardly through an inner portion of the partition member, thesecond orifice passage being open to the pressure-receiving chamberthrough a first opening formed at an outer peripheral side of themovable partition member in the partition member and being open to theequilibrium chamber through a second opening formed at a central portionof the partition member; and wherein the flexible layer is superimposedonto the second opening of the second orifice passage to constitute thevalve member, the valve member being driven by the actuator to carry outopening/closing control of the second orifice passage by alternatelyopening and closing the second opening of the second orifice passage.

In this embodiment, the first and second orifice passages are formedutilizing the partition wall member that divides the pressure receivingchamber and the equilibrium chamber, and the movable partition member isdisposed, whereby the members are functionally situated so as realize acompact construction overall.

According to the sixth advantageous form of the invention, an elasticcontact projection is formed projecting out from an outer peripheraledge portion of the center movable plate portion in the movablepartition member, the elastic contact projection being positioned intcontact against the second mounting member or a displacement restrictingmember supported by the second mounting member, thereby providingdisplacement limiting member for cushion-wise limitation of an extent ofdisplacement of the center movable plate portion.

In this advantageous form, the displacement limiting member makes itpossible to more effectively suppress absorption of pressurefluctuations of the pressure receiving chamber by the movable partitionmember, during input not only of low frequency, large amplitudevibration but also of low frequency, small amplitude vibration. This mayincrease the flow volume of fluid induced to flow through the firstorifice passage, thereby improving damping action based on resonanceaction of the fluid, and vibration damping performance against lowfrequency vibration in association therewith. Further, since it ispossible to adjust the support spring characteristics of the centermovable plate portion by means of contact of the elastic contactprojection against the second mounting member or the displacementrestricting member, it becomes possible to adjust the characteristicfrequency of the center movable plate portion to coincide with a highfrequency vibration frequency range corresponding to driving boomingnoise, or the like. Additionally, the displacement restricting membercontacted by the elastic contact projection can be advantageouslyconstituted by being fixedly supported by means of the second mountingmember. More specifically, it can be advantageously constituted byutilizing the aforementioned partition member which is fixedly supportedby the second mounting member, and divides the pressure receivingchamber and the equilibrium chamber.

According to the seventh advantageous form of the invention, thepneumatic actuator is operable such that during driving of anautomobile, the valve member is driven by generally atmospheric pressureapplied from an outside whereby the second orifice passage assumes aclosed state thereof, and when the automobile is at a stop the valvemember is driven by negative pressure applied from the outside wherebythe second orifice passage assumes an open state.

This advantageous form makes it possible to switch the second orificepassage between open/closed states by skillfully utilizing the negativepressure from an air intake system of the automobile's internalcombustion engine. Also, in this embodiment, in association withswitching the second orifice passage between open/closed states simplythrough application of positive/negative air pressure and control ofsame to the pneumatic actuator, various types of vibration dampingperformance can be exhibited selectively, whereby simplified controloverall can be advantageously achieved.

According to the eighth advantageous form of the invention, a rigidconstriction plate is disposed in the center movable plate portion ofthe movable partition member, with the outer peripheral rubber filmportion being bonded to the constriction plate.

In this embodiment, the constriction plate makes it possible to morereliably suppress absorption of pressure fluctuations of the pressurereceiving chamber during low- to medium-frequency vibration input due tounwanted deformation of the center movable plate portion. With thisarrangement, it is possible to more effectively and consistently achievedesired vibration damping action based on flow action, e.g. resonanceaction, of fluid induced to flow through the fist orifice passage andsecond orifice passage. The constriction plate will preferably consistof a thin plate of rigid synthetic resin material, metal, or the like.It is possible for the center movable plate portion to consist of theconstriction plate only, with the peripheral movable rubber film portionbonded to the outer peripheral edge thereof. Alternatively, it ispossible to bond the constriction plate to the center portion of arubber elastic film that extends over substantially the entire centermovable plate portion to form the center movable plate portion in thecenter portion of the rubber elastic film, with the peripheral movablerubber film portion being formed by the outer peripheral edge of therubber elastic film.

According to the ninth advantageous form of the invention, displacementand deformation characteristics of the movable partition member aredesigned so that, in the event that input vibration applied across thefirst mounting member and the second mounting member is very smallamplitude vibration of ±0.05 mm or less, pressure fluctuations producedin the pressure receiving chamber can be substantially absorbed; whereasin the event that input vibration applied across the first mountingmember and the second mounting member is small amplitude vibration ofabout ±0.1 mm or large amplitude vibration of ±1.0 mm or more, pressurefluctuations produced in the pressure receiving chamber cannot besubstantially absorbed.

This advantageous form of the invention makes it possible to effectivelyachieve excellent vibration-damping action against a variety ofvibrations that are typically a problem for most automobiles, whilediffering by model. Namely, the present engine mount is capable ofexhibiting excellent vibration damping performance through high dampingaction for (1) low-frequency, large-amplitude vibration in alow-frequency range of around 10 Hz and large amplitude on the order of±1.0 mm, such as by engine shake etc. caused by driving over a speedbump or the like, and (2) low-frequency, small-amplitude vibration in alow-frequency range of around 10 Hz and small amplitude on the order of±0.1 mm, such as engine shake which is a problem during normal driving,while exhibiting excellent vibration damping performance through lowdynamic spring constant or characteristics against (3) booming noise andother high-frequency vibration which is a problem during normal driving,falling in a high-frequency range of from 50 Hz to several hundred Hzand very small amplitude of ±0.05 mm or less. Design displacement anddeformation characteristics on the part of the movable partition memberin the manner described above can be advantageously achieved, forexample, by tunig the characteristic frequency of the movable partitionmember to a frequency range of very small amplitude of ±0.05 mm or less,and utilizing the resonance action of the movable partition member; orby employing the displacement restricting member in the aforementionedfifth advanttageous form of the invention.

As will be apparent from the preceding description, since thepneumatically switchable type fluid filled engine mount of constructionin accordance with the present invention employs a movable partitionmember composed of a center movable plate portion and an outerperipheral rubber film portion, the desired vibration-dampingcapabilities against vibration of multiple, wide frequency ranges may beachieved with a relatively simple construction, and productionefficiency and cost performance may be advantageously improved.Additionally, the overall control system may be simplified, whereby theprocedure of installation in an automobile may be made easier, andoperating costs may be advantageously reduced.

Further, since the pneumatically switchable type fluid filled enginemount of construction in accordance with the present invention employsthe movable partition member composed of a center movable plate portionand an outer peripheral rubber film portion, vibration-attenuatingeffect against low- or medium-frequency vibration is advantageouslyachieved based on resonance action of fluid through the first or secondorifice passage, and vibration isolating effect against high-frequencyvibration is advantageously achieved based on liquid pressure absorbingaction of the movable partition member, whereby the desiredvibration-damping capabilities against vibration of multiple, broadfrequency ranges may be advantageously achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and/or other objects features and advantages of theinvention will become more apparent from the following description of apreferred embodiment with reference to the accompanying drawings inwhich like reference numerals designate like elements and wherein:

FIG. 1 is a vertical cross sectional view of a fluid-filed engine mountof construction according to a first embodiment of the invention, takenalong line 1-1 of FIG. 2;

FIG. 2 is a top plane view of a partition member of the engine mount ofFIG. 1;

FIG. 3 is a bottom plane view of the partition member of FIG. 2;

FIG. 4 is a perspective view of the partition member of FIG. 2;

FIG. 5 is a top plane view of a movable member of the engine mount ofFIG. 1;

FIG. 6 is a bottom plane view of the movable member of FIG. 5;

FIG. 7 is a top plane view of a constriction plate of the engine mountof FIG. 1;

FIG. 8 is a top plane view of a cover plate fitting of the engine mountof FIG. 1;

FIG. 9 is an enlarged fragmentary view in vertical cross section of apart of the engine mount of FIG. 1;

FIG. 10 is an enlarged fragmentary view in vertical cross section ofanother part of the engine mount of FIG. 1;

FIG. 11 is a graph showing measurements of dynamic characteristics ofthe engine mount of FIG. 1 (Example 1), and measurements of dynamiccharacteristics of the engine mount of FIG. 1 with the second orificepassage of different construction (Example 2);

FIG. 12 is a vertical cross sectional view of a fluid-filled enginemount of construction according to a second embodiment of the invention,taken along line 12-12 of FIG. 13;

FIG. 13 is a top plane view of a partition member of the engine mount ofFIG. 12;

FIG. 14 is a bottom plane view of the partition member of FIG. 13;

FIG. 15 is a perspective view of the partition member of FIG. 13;

FIG. 16 is a top plane view of a movable member of the engine mount ofFIG. 12;

FIG. 17 is a bottom plane view of the movable member of FIG. 16;

FIG. 18 is a top plane view of a constriction plate of the engine mountof FIG. 12;

FIG. 19 is a top plane view of a cover plate fitting of the engine mountof FIG. 12;

FIG. 20 is an enlarged fragmentary view in vertical cross section of apart of the engine mount of FIG. 12; and

FIG. 21 is an enlarged fragmentary view in vertical cross section ofanother part of the engine mount of FIG. 12.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The preferred embodiments of the invention are described in detailhereinbelow with reference to the accompanying drawings, in order toprovide a more specific understanding of the invention. Referring firstto FIG. 1, there is illustrated an automotive vibration damping enginemount 10 as an embodiment of the invention. This engine mount 10 has aconstruction wherein a first mounting member in the form of a firstmount fitting 12, and a second mounting member in the form of a secondmount fitting 14, are elastically connected by means of a rubber elasticbody 16, with the first mount fitting 12 attached to the power unitside, and the second mount fitting 14 attached to the vehicle body side,to support the power unit of the body in a vibration-damped manner. Inthe description hereinbelow, vertical direction shall refer to thevertical direction in FIG. 1.

To describe in more detail, the first mount fitting 12 has a block shapeof generally inverted truncated cone form. A mount bolt 20 is integrallyformed on the large-diameter end face thereof, projecting upward in theaxial direction.

The second mount fitting 14, on the other hand, has a large-diameter,generally cylindrical shape overall. The second mount fitting 14 has anecked portion 22 at is upper axial end. This necked portion 22 recessesinwardly in the diametrical direction and extends about the entirecircumference in the circumferential direction. By means of the neckedportion 22, the open end at the upper axial end of the second mountfitting 14 is given an inverted taper shape that expands graduallymoving upward. The first mount fitting 12 is disposed generallycoaxially with the second mount fitting 14, while being spaced apartfrom the necked portion 22 of the upper open end thereof. The rubberelastic body 16 is disposed between the first mount fitting 12 and thesecond mount fitting 14 with these fittings being elastically coupled bymeans of the rubber elastic body 16.

The rubber elastic body 16 has a generally truncated cone shape overall,with the first mount fitting 12 inserted into the rubber elastic body 16from the small-diameter end thereof and bonded by vulcanization thereto.The open end portion at the axial upper end of the second mount fitting14 overlaps the outside peripheral face of the large-diameter end of therubber elastic body 16 and is vulcanization bonded thereto. With thisarrangement, the tapered outer peripheral face of the first mountfitting 12 and the inverted taper shaped inner peripheral face of thenecked portion 22 of the second mount fitting 14 are positioned inopposition to one another, with the rubber elastic body 16 interposedbetween the opposed faces. In this embodiment, the rubber elastic body16 is an integrally vulcanization molded component comprising the firstmount fitting 12 and the second mount fitting 14.

With the outside peripheral wall of the rubber elastic body 16 bonded byvulcanization to the opening of the second mount fitting 14, the openingon the axial upper end of the second mount fitting 14 is provided withfluid-tight closure by the rubber elastic body 16. On the large-diameterend of the rubber elastic body 16 there is formed a large-diameterrecess 24 of cone shape, opening into the second mount fitting 14.

A seal rubber layer 26 is formed covering the inner peripheral face ofthe second mount fitting 14. This seal rubber layer 26 is integrallyformed with the rubber elastic body 16, and substantially the entireinner peripheral face of the second mount fitting 14 is covered by theseal rubber layer 26.

A partition member 28 and a rubber diaphragm 30 serving as the flexiblelayer are fitted in sequence into the second mount fitting 14 from theopening at the bottom axial end, and fastened fitting within the secondmount fitting 14. A cylindrical fastening cylinder fitting 32 isvulcanization bonded to the outer peripheral edge of the rubberdiaphragm 30, and this fastening cylinder fitting 32 is fastened fittingwithin the lower mount of the second mount fitting 14 to providefluid-tight closure to the lower opening of the second mount fitting 14.

By means of this arrangement, to one side of the partition member 28(the upper side in FIG. 1), there is formed a pressure receiving chamber34 whose wall is partially composed of the rubber elastic body 16. Tothe other side of the partition member 28 (the lower side in FIG. 1),there is formed an equilibrium chamber 36 whose wall is partiallycomposed of the rubber diaphragm 30. The pressure receiving camber 34,and the equilibrium chamber 36 have sealed therein a non-compressiblefluid such as water, an alkylene glycol, a polyalkylene glycol, siliconeoil, or the like. In the pressure receiving chamber 34 positive pressurefluctuations are produced on the basis of elastic deformation of heerubber elastic body 16 when vibration is input, whereas in theequilibrium chamber 36, deformation of the rubber diaphragm 30 isreadily allowed so that capacity is variable, whereby pressurefluctuations can be absorbed promptly.

As shown in FIGS. 2-4, the partition member 28 comprises a divider block38 having a thick, generally disk shape. The divider block 38 has formedrespectively in the center portions of its upper end face and lower endface an upper central recess 40 and a lower central recess 42, each withthe form of a generally circular depression.

In the divider block 38 is also formed a circumferential groove 44 thatopens onto the outer peripheral face of the divider block 38 and thatextends in the circumferential direction. Each of the two ends of thiscircumferential groove 44 open in the face of the divider block 38 onone side in the axial direction. Also formed in the divider block 38 isan axial groove 46 that opens onto the outer peripheral face of thedivider block 38 and that extends in a straight line over apredetermined distance in the axial direction. The upper end of thisaxial groove 46 utilizes one end of the circumferential groove 44 toopen in the upper face of the divider block 38.

The lower end of the axial groove 46 connects to the lower centralrecess 42 through a connecting hole 48 that extends in a tunnelconfiguration in the diametrical direction. That is, the connecting hole48 at its first end opens into the lower central recess 42 through anopening 50 of rectangular shaped in a side view, which is formed in thecenter portion of the divider block 38. The other end of the connectinghole 48 opens onto the outer peripheral face of the divider block 38 viathe open and of the axial groove 46.

In this embodiment in particular, the width dimension of the connectinghole 48 in the circumferential direction increases gradually goingoutwardly in the diametrical direction (axis-perpendicular direction)from the opening 50 connected to the lower central recess 42 towards theouter peripheral face of the partition member 28. By means of thisdesign, the cross sectional area in the connecting hole 48 in thediametrical direction extending from the opening 50 towards the axialgroove 46 is given a shape that becomes gradually larger in thecircumferential direction or width dimension moving diametricallyoutward from the opening 50.

Additionally, the upper central recess 40 of the divider block 38 isprovided in the depthwise medial portion thereof with a stopped face 52,thereby forming a stepped circular recess composed of a small-diameterrecess portion 54 towards the floor end and a large-diameter recessportion 56 towards the opening end. An annular recess 58 of generallyring shape seen in plan view is formed extending continuously around theentire circumferential direction of the axially medial portion. Theannular recess 58 connects to the small-diameter recess 54 throughconnector slots 60 formed at several locations (two locations in thisembodiment) in the inner peripheral wall. Also formed in the peripheralwall of the small-diameter recess 54 is an air passage 62 extendingthrough the divider block 38 in the diametrical direction. The insideend of this air passage 62 communicates with the small-diameter recess54, while the outside end of the air passage 60 opens to the outside atthe outer peripheral face of the divider block 38.

A movable member 64 serving as the movable partition member is assembledwith the large-diameter recess portion 56. From the top of the movablemember 64, a cover plate fitting 66 is assembled overlapping the upperface of the divider block 38.

As illustrated in the single component diagrams in FIGS. 5 and 6, themovable member 64 has a rubber elastic plate 68 of circular, generallythin plate shape, with a circular mating fitting 70 vulcanization bondedto the outer peripheral face of this rubber elastic plate 68. The matingfitting 70 is secured press-fit into the large-diameter recess portion56 of the divider block 38, whereby the upper central recess 40 isprovided with fluid-tight closure by the movable member 64, thus formingthe pressure receiving chamber 34 above the movable member 64 on the oneband, while forming an air chamber 72 below the movable member 64. Theair chamber 72 normally communicates with the atmosphere via the airpassage 62 formed in the divider block 38, and through-holes formedpassing through the peripheral wall of the second mount fitting 14 and abracket 18.

The rubber elastic plate 68, in a portion thereof situated generally atthe inner peripheral edge of the stepped face 52 of the divider block3S, has an integrally formed annular elastic projection 74 that extendscontinuously or discontinuously in the circumferential direction. Atseveral locations on the circumference of the elastic projection 74(four locations in this embodiment) are integrally formed contactsupport portions 76 of generally trapezoid configuration that projectappreciably from the upper and lower faces. In this embodiment, thedistal edge-to-edge dimension of elastic projection 74, 74 is designedto be slightly smaller than the axial dimension of the mating fitting70, and the distal edge-to-edge dimension of the contact supportportions 76, 76 is designed to be the same as or slightly larger thanthe axial dimension of the mating fitting 70.

A rigid constriction plate 78 consisting of metal or synthetic resin isembedded in the center portion of the rubber elastic plate 68. As shownin FIG. 7, this constriction plate 78 is of generally shallow dish shapewhose center portion is slightly recessed, and while thin, providesimproved deformation rigidity. The constriction plate 78 has an outsidediameter dimension larger than the inside diameter dimension of theupper central recess 40 of the divider block 38, with the outerperipheral edge of the constriction plate 78 extending out to thestepped face 52.

A notch 80 is formed at each of several locations on the outerperipheral edge of the constriction plate 78 corresponding to the upperand lower contact support portions 76, 76 to provide clearance at thelocations where the contact support portions 76, 76 are formed when theconstriction plate 78 is covered by the rubber elastic plate 68. Thecenter of the constriction plate 78 is perforated by circular hole 82and covered by the rubber material making up the movable member 64.Forming this circular hole 82 affords good distribution of rubbermaterial onto both faces of the constriction plate 78 and also improvesbond strength of the rubber to the constriction plate 78. By adjustingthe size of the circular hole 82 and the thickness dimension of therubber film closing off the circular hole 82, it is possible toappropriately adjust the elastic deformation characteristics of themovable member 64.

The outer peripheral portion of the rubber elastic plate 68 is made thinin the portion situated between the elastic projection 74 and the matingfitting 70. By means of this design, an outer peripheral movable rubberfilm portion 84 is formed with an annular disk configuration extendingover predetermined width in the circumferential direction. This outerperipheral movable rubber film portion 84 is positioned on the opting ofthe annular recess 58 formed at the stepped face 52 of the divider block38.

On the other hand, as shown in FIG. 8, the cover plate fitting 66 hasthe overall form of a thin, generally disk shaped member having a slightstepped portion 86 formed in the diametrically medial portion, and has acenter portion projecting downward with respect to the outer peripheraledge portion. The cover plate fitting 66 is superposed onto the upperface of the divider block 38, and the stepped portion 86 is fitted intothe opening of the upper central recess 40 of the divider block 38 toattach it positioned in the diametrical direction.

A round center through-hole 88 is formed in the center portion of thecover plate fitting 66, and around this center through-hole 88 areformed a number of outer peripheral through-holes 90 that extend apredetermined width in the circumferential direction. When the coverplate fitting 66 is installed on the divider block 38, a center movableplate portion 92 of the rubber elastic plate 68 reinforced by theconstriction plate 78 faces the pressure receiving chamber 34 throughthe center through-hole 88, and the outer peripheral movable rubber filmportion 84 faces the pressure receiving chamber 34 through the outerperipheral through-holes 90.

A notched window 94 is provided at single circumferential location onthe outer peripheral edge of the cover plate fitting 66, this notchedwindow 94 being positioned aligned with the upper opening shared by thecircumferential groove 44 and the axial groove 46 provided to thedivider block 38. In order to position the notched window 94 and grooves44, 46 aligned with one another, a positioning projection 96 is disposedat an appropriate location on the circumference of the upper end face ofthe divider block 38, and a positioning hole 98 is formed at acorresponding location on the cover plate fitting 66, with positioningin the circumferential direction being realized through the matingaction of the positioning projection 96 and the positioning hole 98.

With the aforementioned rubber elastic plate 68 and cover plate fitting66 attached to the divider block 38, as shown in enlarged view in FIG.9, the contact support portions 76 of the rubber elastic plate 68 aredisposed with the distal end faces thereof contacting the stepped face52 of the divider block 38 or the lower face of the cover plate fitting66, and appropriately compressed where necessary. As shown in enlargedview in FIG. 10, the elastic projection 74 is positioned across a slightgap from the stopped face 52 of the divider block 38 or the lower faceof the cover plate fitting 66. When a pressure fluctuation of thepressure receiving chamber 34 is exerted against the rubber elasticplate 68, the rubber elastic plate 68 undergoes displacement anddeformation on the basis of the pressure difference between the pressurereceiving chamber 34 and the air chamber 72 exerted across the upper andlower faces of the rubber elastic plate 68. In this embodiment, theelastic projection 74 functions as an elastic contact projection and isbrought into contact against a displacement restricting member in theform of the cover plate fitting 66, thereby providing displacementlimiting member for cushion-wise limitation of an extent of displacementof the center movable plate portion 92.

With this arrangement, deformation of the center movable plate portion92 of the rubber elastic plate 68 is limited by the constriction plate78 embedded therein. Thus, the displacement will be occurred principallybased on elastic deformation of the contact support portions 76, 76. Theouter peripheral movable rubber film portion 84 is thin and readilyallows elastic deformation, so that displacement is produced due to thisdeformation. The space of the back of the center movable plate portion92 and the space to the back of the outer peripheral movable rubber filmportion 84 are consistently maintained in a communicating state by theconnector slots 60, and function substantially like a single airchamber. In this embodiment, the intermediate equilibrium chamber isconstituted by this air chamber.

The openings of the circumferential groove 44 and the axial groove 46formed on the outside peripheral face of the divider block 38 are eachprovided with fluid-tight closure by the second mount fitting 14. Byproviding closure to the circumferential groove 44, there is formed afirst orifice passage 100 connecting the pressure receiving chamber 34and the equilibrium chamber 36 to one another. This passage is normallyin the open state. By providing closure to the axial groove 46, there isformed a second orifice passage 102 that passes from the connecting hole48 to the lower central recess 42 of the divider block 38, and opensinto the equilibrium chamber 36 to connect the equilibrium chamber 36 tothe pressure receiving chamber 34.

This second orifice passage 102 is formed with approximately the samepassage cross sectional area as the first orifice passage 100, butshorter passage length. By means of this design, the second orificepassage 102 is tuned to a higher frequency range than the first orificepassage 100. Specifically, the resonance frequency of fluid caused toflow through the first orifice passage 100 is tuned so as to exhibit, onthe basis of resonance action of the fluid, high damping characteristicsagainst engine shake or other low-frequency, small-amplitude vibrationon the order of ±0.1 mm and 10 Hz, and engine shake or otherlow-frequency, large-amplitude vibration on the order of ±1.0 mm and 10Hz, for example. The resonance frequency of fluid caused to flow throughthe second orifice passage 102 is tuned so as to exhibit, on the basisof resonance action of the fluid, low dynamic spring constant againstidling vibration or other medium-frequency, medium amplitude vibrationon the order of ±0.1-0.25 mm and 20-40 Hz, for example. Thecharacteristic frequency of die movable member 64, based on displacementand deformation of the movable member 64, is tuned so that the movablemember 64 is effectively made to produce resonance phenomenon againstdriving booming noise or other high-frequency, very small amplitudevibration on the order of ±0.01-0.02 mm and 60-120 Hz, for example.

In this embodiment in particular, since the diametrical cross sectionalarea of the connecting hole 48 that constitutes part of the secondorifice passage 102 gradually expands in the circumferential directiongoing diametrically outward from the opening 50 formed in the centerportion of the divider block 38, the capacity of the second orificepassage 102 is greater than the capacity of a second orifice passageimparted with a structure of straight shape over the entire lengththereof that extends with a generally constant size diametricallyoutward from the opening.

As described above, the mount body is formed by attaching the partitionmember 28 and rubber diaphragm 30 to the integrally vulcanization moldedcomponent of the rubber elastic body 16 having the first mount fitting12 and the second mount fitting 14. To this mount body, there isadditionally attached a bracket 18. The bracket 18 has a large-diameter,deep-bottomed generally bottomed cylindrical shape overall, and isfastened fitting onto the exterior of the second mount fitting 14. Thebracket 18 is then secured press-fit into a cylindrical fastener fitting104 having a large-diameter, generally cylindrical shape, thecylindrical fastener fitting 104 being bolted to the vehicle body,whereby the second mount fitting 14 is mounted onto the vehicle body bymeans of the bracket 18.

The bracket 18 is sufficiently deep-bottomed relative to the secondmount fitting 14, and with the second mount fitting 14 secured fittingtherein, there is formed an internal space 106 of sufficient sizelocated in the lower portion of the bracket 18. By means of thisinternal space 106 the rubber diaphragm 30 is permitted to undergo buingdeformation to a sufficiently large extent.

Also disposed in the lower portion of the bracket 18 is a pneumaticactuator 108. This pneumatic actuator 108 utilizes the floor of thebracket 18 as a base housing 110, and is attached to the base housing110 so that an output member 112 serving as the valve member ispositioned inside the bracket 18.

The output member 112 comprises a divider rubber 114 of generally hatshape overall, with the center portion of the divider rubber 114constituting an output portion 116 of inverted cup shape, and with theouter peripheral portion constituting a tapered, flange shaped elasticperipheral wall portion 118 that flares downward on the diagonal fromthe rim at the lower end of the output portion 116. The output portion116 has embedded therein a rigid reinforcing member 120 formed of metalor synthetic resin, while an annular press-fitting fixture 122 is bondedby vulcanization to the outer peripheral edge of the peripheral wallportion 118.

By press fitting the press-fitting fixture 122 against the bottomperipheral wall of the bracket 18, the outer peripheral edge of thedivider rubber 114 is placed in fluid-tight contact against the bottomface of the base housing 110 formed by the bracket 18. With thisarrangement, the opening of the output member 112 is provided closure bythe bottom wall of the base housing 110 to constitute a pneumaticactuator 108 with a pressure regulating air chamber 124 formed inside.

In this embodiment, a compressed coil spring 126 is attachedaccommodated within the pressure regulating air chamber 124 so thaturging force is normally exerted in the direction pushing the outputportion 116 and the base housing 110 apart from one another. An air port128 passes through the center of the floor of the base housing 110.Pressure in the pressure regulating air chamber 124 can be controlledfrom the outside through this air port 128.

With the engine mount 10 installed, an external air pressure line 130 isconnected to the air port 128, and a switch valve 132 is connected viathe air pressure line 130. In accordance with switching operation of theswitch valve 132, the pressure regulating air chamber 124 is selectivelyconnected to the atmosphere or a negative pressure source 134.

With the pressure regulating air chamber 124 connected to theatmosphere, by means of the action of the elastic behavior of theelastic peripheral wall portion 118 and the elastic behavior of thecompressed coil spring 126 on the output portion 116, the output portionis caused to project resiliently upward, urging the rubber diaphragm 30upward and holding it pressed against the center lower face of thedivider block 38 in the partition member 28. Since the contour of theoutput portion 116 is larger than the opening diameter of the lowercentral recess 42 formed on the center lower face of the divider block38, the center portion of the rubber diaphragm 30 is pushed against theopening of the lower central recess 42 and provides substantiallyfluid-tight closure thereto, whereby the second orifice passage 102which opens into the equilibrium chamber 36 through the lower centralrecess 42 is closed off.

On the other hand, with the pressure regulating air chamber 124connected to the negative pressure source 134, on the basis of thepressure differential between outside atmospheric pressure and thenegative pressure exerted inside the pressure regulating air chamber124, the output portion 116 is drawn into the pressure regulating airchamber 124 in opposition to the elastic behavior of the elasticperipheral wall portion 118 and the elastic behavior of the compressedcoil spring 126, causing it to become displaced axially downward. Thus,the rubber diaphragm 30 separates from the opening of the lower centralrecess 42, opening the second orifice passage 102 and placing it in theopen state.

In this embodiment, the switch valve 132 is switched by the controller136 according to whether the vehicle is driving or at a stop. That is,during driving, the pressure regulating air chamber 124 is connected tothe atmosphere, whereas when at a stop, the pressure regulating airchamber 124 is connected to the negative pressure source 134. Thecontroller 136 is advantageously constituted so as to output a drivecontrol signal to an electromagnetic solenoid constituting the switchvalve 132, by means of an acceleration sensor or the like.

Accordingly, in the engine mount 10 of the construction described above,low frequency, large amplitude vibration input when driving over a speedbump or the like is not accompanied by absorption of liquid pressurethrough displacement and deformation of the movable member 64 comprisingthe center movable plate portion 92 and the outer peripheral movablerubber film portion 84, so that effective pressure fluctuation isproduced in the pressure receiving chamber 34. By means of this, arelative pressure fluctuation between the pressure receiving chamber 34and the equilibrium chamber 36 is effectively produced. Thus, as long asthe second orifice passage 102 is maintained in the closed state by theoutput member 112, fluid flow volume through the first orifice passage100 is advantageously assured, a high level of damping effect based onflow action, e.g. resonance action, of the fluid induced to flow throughthe first orifice passage 100 is exhibited, and excellent vibrationdamping ability is achieved,

In response to low frequency, small-amplitude vibration input duringnormal driving, as with the low frequency, large-amplitude vibrationdescribed earlier, as long as the second orifice passage 102 ismaintained in the closed state by the output member 112, fluid flowvolume through the first orifice passage 100 is advantageously assured,a high level of attenuating effect based on flow action, e.g. resonanceaction, of the fluid induced to flow through the first orifice passage100 is exhibited, and excellent vibration damping ability is achieved.While pressure absorption of the pressure receiving chamber 34 by themovable member 64 is a concern, in this embodiment, the fact thatfluid-tightness at the outer peripheral side of the center movable plateportion 92 is assured by the outer peripheral movable rubber filmportion 84, and the fact that the extent of deformation of the movablemember 64 is suppressed by the rigidity of the center movable plateportion 92, mean that adequate pressure fluctuations are created in thepressure receiving chamber 34.

Since pressure fluctuations of the pressure receiving chamber 34 inresponse to high-frequency, very small amplitude vibration input duringdriving are extremely small, the pressure fluctuations of the pressurereceiving chamber 34 are effectively absorbed and lessened by means ofdisplacement and deformation of the movable member 64. In particular,since the center movable plate portion 92 of the movable member 64 canbe formed in the center portion to advantageously assure effectivesurface area, whereas the outer peripheral edge portion thereof isconstituted as fluid-tightly supported, readily deformable outerperipheral movable rubber film portion 84, following displacement inresponse to high frequency pressure fluctuations in the pressurereceiving chamber 34 can advantageously be achieved, and pressurefluctuations in the pressure receiving chamber 34 can be suppressed.Additionally, since the characteristic frequency of the movable member64 is tuned to the high frequency range of vibration to be damped, whenhigh frequency vibration is input, the movable member 64 moreadvantageously undergoes following displacement on the basis ofresonance action. Thus, when high frequency vibration is input, evenwith the first and second orifice passages 100, 102 in substantiallyclosed states, sharp pressure fluctuations in the pressure receivingchamber 34 can be avoided by the movable member 64, and excellentvibration damping action may be achieved by means of effective vibrationisolating action based on low dynamic spring characteristics.

Further, in response to medium-frequency, medium-amplitude vibrationinput with the vehicle at a stop, while pressure absorption of thepressure receiving chamber 34 by the movable member 64 is a concern, inthis embodiment, since the extent of deformation of the movable member64 is suppressed on the basis of the rigid center movable plate portion92 disposed in the center portion of the movable member 64, and sincethe outer peripheral movable rubber film portion 84 is disposed to theoutside of the center movable plate portion 92 ensuring that thepressure receiving chamber 34 is fluid-tight, adequate pressurefluctuations are created in the pressure receiving chamber 34. Thus, bymeans of operation of the pneumatic actuator 108 placing the secondorifice passage 102 in the open state, an adequate level of fluid flowthrough the second orifice passage 102 can be adequately assured,whereby high damping effect based on flow action, e.g. resonance action,of the fluid induced to flow through the second orifice passage 102 isacheved, and excellent vibration damping ability is exhibited.Additionally, with the second orifice passage 102 in the open state, thefirst orifice passage 100 is in the open state as well, but sincemedium-frequency input vibration of a frequency range above of thetuning frequency of the first orifice passage 100 will be countered bythe first orifice passage 1100 becoming substantially closed due toantiresonant action of fluid through the first orifice passage 100, thelevel of fluid flow through the second orifice passage 102 iseffectively assured.

Accordingly, in the engine mount 10 of this embodiment, the firstorifice passage 100, second orifice passage 102, and movable member 64each function efficiently in response to the frequency and amplitude ofvibration to be damped, whereby effective vibration damping action isexhibited against vibration of multiple, wide frequency ranges

In the embodiment, by employing a movable member 64 that comprises acenter movable plate portion 92 and an outer peripheral movable rubberfilm portion 84, when a mode requiring suppression of liquid pressureabsorption of the pressure receiving chamber 34 by the movable member 64so that pressure fluctuations are effectively produced in the pressurereceiving chamber 34, e.g. during input of low-frequency,small-amplitude vibration or medium-frequency, medium-amplitudevibration as described previously, based on the fact that the extent ofdeformation of the movable member 64 is suppressed by the rigid centermovable plate portion 92 formed in the center of the movable member 64,and the fact that fluid-tightness to the outside of the center movableplate portion 92 is assured by the outer peripheral movable rubber filmportion 84, effective pressure fluctuations are produced in the pressurereceiving chamber 34. Thus, since adequate fluid flow levels through thefirst orifice passage 100 or second orifice passage 102 are assured, byselectively switching the second orifice passage 102 between the openstate and the closed state, vibration damping effect based on fluid flowaction through the orifice passages 100, 102 can be advantageouslyachieved.

As a result, even in the absence of a construction whereby, for example,air pressure from the outside (either negative pressure or positivepressure) is exerted to cause the movable member 64 to undergoconstricting deformation and suppress the liquid pressure absorbingaction thereof, the desired vibration damping effect can nevertheless beachieved on the basis of suppressing the extent of deformation anddisplacement by means of the construction of the movable member 64 sothat pressure fluctuations are effectively produced in the pressurereceiving chamber 34. Thus, the overall structure can be realizedfunctionally, production efficiency can be advantageously improved, andthe construction of the switch valve 132, the controller 136, the airpressure line 130 etc. can be simplified, thereby advantageouslyreducing production costs and operating costs, as well as simplifyinginstallation in an automobile.

In this embodiment, by giving the connecting hole 48 that constitutespart of the second orifice passage 102 a flaring shape whose widthdimension in the circumferential direction increases gradually goingdiametrically outward from the opening 50 formed in the center portionof the divider block 38, large capacity on the part of the secondorifice passage 102 is assured. As a result, in situations wherevibration damping characteristics involving effective pressurefluctuations being produced in the pressure receiving amber 34 arerequired, even in the event that a predetermined level of pressureabsorption of the pressure receiving chamber 34 by the movable member 64is produced, an adequately high level of flow of fluid caused to flowthrough the second orifice passage 102 is assured, whereby the desiredvibration damping effect (high damping effect) is exhibited on the basisof flow action of fluid through the second orifice passage 102.

Additionally, in this embodiment, by forming the elastic projection 74and the contact support portions 76 as elastic contact projections onthe movable member 64, the extent of displacement of the movable member64 can be limited, more effectively suppressing pressure absorption bythe movable member 64 during input of low-frequency, small-amplitudevibration.

In the engine mount 11 of this embodiment, since the constriction plate78 is secured embedded in the center movable plate portion 99 of themovable member 64, it is possible to more reliably suppress absorptionof pressure fluctuations of the pressure receiving chamber 34 duringlow- to medium-frequency vibration input due to unwanted deformation ofthe center movable plate portion 92, whereby vibration damping actionbased on flow action in the first orifice passage and second orificepassage is effectively exhibited.

Results of actual measurements of the frequency characteristics ofvibration damping ability (dynamic absolute spring constant) taken forthe engine mount 10 constructed according to the embodiment hereinaboveare presented in the graph of FIG. 11 as Example 1. Frequencycharacteristics of vibration damping ability, measured in the same wayas for Example 1, but for a engine mount (not shown) constructed with astraight shape over its entire length by means of extending thediametrical cross sectional area of the connecting hole constitutingpart of the second orifice passage with generally constant sizediametrically outward from the opening formed in the center portion ofthe divider block, are also shown in FIG. 11, as Example 2. In Example1, the diametrical cross sectional area of the opening of extendedrectangular shape in side view, which opens onto the outside peripheralface of the divider block 38 in the connecting hole 48, is 225 mm²,whereas in Example 2 it is 147 mm². In Example 1, the passage lengthextending diametrically outward from the opening 50 of the secondorifice passage 102, to the opening which opens onto the outsideperipheral face of the divider block 38 is 40 mm, whereas in Example 2it is 41 mm. With this arrangement, the capacity of the second orificepassage 102 pertaining to Example 1 is larger than the capacity of thesecond orifice passage 102 pertaining to Example 2. During measurement,a static initial load of 1000 N equivalent to the distributed supportload of a power unit was applied across the first mount fitting 12 andthe second mount fitting 14, and vibration of 0.25 mm amplitude(displacement) approximating engine shake (small amplitude) and idlingwas applied.

As will be apparent from the results shown in FIG. 11, in the enginemounts pertaining to Examples 1 and 2, in response to vibration in amedium-frequency range of 20-40 Hz, which is one of the vibrationfrequency ranges needing to be damped, resonance phenomenon of thesealed fluid effectively occurs in each, and sufficient improvement invibration damping ability based on resonance action or other flow actionof the fluid could be expected in the vibration frequency range inquestion.

It will also be apparent from the results in FIG. 11 that the enginemount 10 pertaining to Example 1 was found to more advantageouslyexhibit high attenuating action against vibration in themedium-frequency range as compared to the engine mount pertaining toExample 2, leading to the conclusion that vibration damping ability inthe frequency range was improved on the basis of ensuring large capacityon the part of the second orifice passage 102.

While the present invention has been described in detail in itspresently preferred embodiments, for illustrative purpose only, it is tobe understood that the invention is by no means limited to the detailsof the illustrated embodiments, but may be otherwise embodied. It isalso to be understood that the present invention may be embodied withvarious changes, modifications and improvements which may occur to thoseskilled in the art, without departing from the spirit and scope of theinvention.

For example, in the embodiment hereinabove, the center movable plateportion 92 is reinforced by embedding a rigid constriction plate 78, butthe constriction plate 78 could be dispensed with. Specifically, bymaking the rubber elastic plate 69 thicker as necessary to impartsufficient rigidity to it, it becomes possible to exhibit functionalityas the center movable plate portion 92, even without being reinforced bythe constriction plate 78.

Also, whereas in the embodiment hereinabove a compressed coil spring 126is used as the urging means for pusbing against the opening of the lowercentral recess 42, the urging means is not limited to that taught in theembodiment. Specifically, it would be possible to instead simply utilizethe elastic behavior of the divider rubber 114 to maintain a state ofcontact, or to use a plate spring or the like instead of a compressedcoil spring 126.

The shape, size, and construction of the center movable plate portion 92and the outer peripheral movable rubber film portion 84 in the movablemember 64, as well as the placement location of the movable member 64with respect to the partition member 28, are not limited to those taughtherein by way of example, and may be modified appropriately depending onthe required vibration damping characteristics, produce-ability, andother considerations. For example, whereas in the embodiment hereinabovethe outer peripheral edge of the movable member 64 is supportedfluid-tightly on the second mount fitting 14 through the agency of thepartition member 28, by means of press-fitting the mating fitting 70vulcanization bonded thereto against the partition member 28, it wouldbe acceptable instead, rather than attaching a mating fitting (70) tothe outer peripheral edge of the movable member 64, to arrange the outerperipheral edge rubber portion forming the outer peripheral edge portionof the movable member 64 so that it is clamped fluid-tightly in theaxial direction, thereby fixedly attaching the outer peripheral edgeportion of the movable member 64 to the second mount fitting 14 via thepartition member 28 if necessary.

Additionally, whereas in the embodiment hereinabove the diametricalcross sectional area of the connecting hole 48 extending from theopening 50 towards the axial groove 46 is of flared shape that graduallyincreases in size in the circumferential direction going from theopening 50 towards the axial groove 46, i.e. going diametricallyoutward, the axial sectional area of the connecting hole 48 could begiven a flared shape that gradually increases in size in the axialdirection going diametrically outward, instead of or in addition to theincreasing diametrical sectional area of the connecting hole 48.

Further, whereas the embodiment hereinabove describes application of theinvention in an automotive engine mount by way of a specific example,the invention could of course be implemented advantageously innon-automotive engine mounts as well,

Referring next to FIG. 12, there is illustrated an automotive vibrationdamping engine mount 210 as an embodiment of the invention. This enginemount 210 has a construction wherein a first mounting member in the formof a first mount fitting 212, and a second mounting member in the formof a second mount fitting 214, are elastically connected by means of arubber elastic body 216, with the first mount fitting 212 attached tothe power unit side, and the second mount fitting 214 attached to thevehicle body side, to support the power unit of the body in avibration-damped manner. In the description hereinbelow, verticaldirection shall refer to the vertical direction in FIG. 12.

To describe in more detail, the first mount fitting 212 has a blockshape of generally inverted truncated cone form. A mount bolt 220 isintegrally formed on the large-diameter end face thereof, projectingupward in the axial direction.

The second mount fitting 214, on the other hand, has a large-diameter,generally cylindrical shape overall. The second mount fitting 214 has anecked portion 222 at is upper axial end. This necked portion 222recesses inwardly in the diametrical direction and extends about theentire circumference in the circumferential direction. By means of thenecked portion 222, the open end at the upper axial end of the secondmount fitting 214 is given an inverted taper shape that expandsgradually moving upward. The first mount fitting 212 is disposedgenerally coaxially with the second mount fitting 214, while beingspaced apart from the necked portion 222 of the upper open end thereof.The rubber elastic body 216 is disposed between the first mount fitting212 and the second mount fitting 214 with these fittings beingelastically coupled by means of the rubber elastic body 216.

The rubber elastic body 216 has a generally truncated cone shapeoverall, with the first mount fitting 212 inserted into the rubberelastic body 216 from the small-diameter and thereof and bonded byvulcanization thereto. The open end portion at the axial upper end ofthe second mount fitting 214 overlaps the outside peripheral face of thelarge-diameter end of the rubber elastic body 216 and is vulcanizationbonded thereto. With this arrangement, the tapered outer peripheral faceof the first mount fitting 212 and the inverted taper shaped innerperipheral face of the necked portion 222 of the second mount fitting214 are positioned in opposition to one another, with the rubber elasticbody 216 interposed between the opposed faces. In this embodiment, therubber elastic body 216 is an integrally vulcanization molded componentcomprising the first mount fitting 212 and the second mount fitting 214.

With the outside peripheral wall of the rubber elastic body 216 bondedby vulcanization to the opening of the second mount fitting 214, theopening on the axial upper end of the second mount fitting 214 isprovided with fluid-tight closure by the rubber elastic body 216. On thelarge-diameter end of the rubber elastic body 216 there is formed alarge-diameter recess 224 of cone shape, opening into the second mountfitting 214.

A seal rubber layer 226 is formed covering the inner peripheral face ofthe second mount fitting 214. This seal rubber layer 226 is integrallyformed with the rubber elastic body 216, and substantially the entireinner peripheral face of the second mount fitting 214 is covered by theseal rubber layer 226.

A partition member 228 and a rubber diaphragm 230 serving as theflexible layer are fitted in sequence into the second mount fitting 214from the opening at the bottom axial end, and fastened fitting withinthe second mount fitting 214. A cylindrical fastening cylinder fitting232 is vulcanization bonded to the outer peripheral edge of the rubberdiaphragm 230, and this fastening cylinder fitting 232 is fastenedfitting within the lower mount of the second mount fitting 214 toprovide fluid-tight closure to the lower opening of the second mountfitting 214.

By means of this arrangement, to one side of the partition member 228(the upper side in FIG. 12), there is formed a pressure receivingchamber 234 whose wall is partially composed of the rubber elastic body216. To the other side of the partition member 228 (the lower side inFIG. 12), there is formed an equilibrium chamber 236 whose wall ispartially composed of the rubber diaphragm 230. The pressure receivingchamber 234 and the equilibrium chamber 236 have sealed therein anon-compressible fluid such as water, an alkylene glycol, a polyalkyleneglycol, silicone oil, or the like. In the pressure receiving chamber 234positive pressure fluctuations are produced on the basis of elasticdeformation of the rubber elastic body 216 when vibration is input,whereas in the equilibrium chamber 236, deformation of the rubberdiaphragm 230 is readily allowed so that capacity is variable, wherebypressure fluctuations can be absorbed promptly.

As shown in FIGS. 13-15, the partition member 228 comprises a dividerblock 238 having a thick, generally disk shape. The divider block 238has formed respectively in the center portions of its upper end face andlower end face an upper central recess 240 and a lower central recess242, each with the form of a generally circular depression.

In the divider block 238 is also formed a circumferential groove 244that opens onto the outer peripheral face of the divider block 238 andthat extends in the circumferential direction. Bach of the two ends ofthis circumferential groove 244 open in the face of the divider block238 on one side in the axial direction. Also formed in the divider block238 is an axial groove 246 that opens onto the outer peripheral face ofthe divider block 238 and that extends in a straight line over apredetermined distance in the axial direction. The upper end of thisaxial groove 246 utilizes one end of the circumferential groove 244 toopen in the upper face of the divider block 238. The lower end of theaxial groove 246 connects to the lower central recess 242 through aconnecting hole 248 that extends in a tunnel configuration in thediametrical direction.

Additionally, the upper central recess 240 of the divider block 238 isprovided in the depthwise medial portion thereof with a stepped face250, thereby forming a stepped circular recess composed of asmall-diameter recess portion 252 on the bottom end and a large-diameterrecess portion 254 on the opening end. An annular groove 256 ofgenerally ring shape seen in plan view is formed in the stepped face250, extending continuously around the entire circumference in thecircumferential direction of the axially medial portion.

Around the lower central recess 242 of the divider block 238, there isformed an annular recess 260 of generally ring shape seen in bottomview, opening in one direction in the axial direction (down in FIG. 12),while leaving a pair of diametrical linking portions 258, 258 thatextend from the outer peripheral wall of the lower central recess 242towards the outer peripheral wall of the divider block 238. With thisarrangement, the peripheral wall of the lower central recess 242 islinked to the outer peripheral wall of the divider block 238substantially exclusively by the pair of diametrical linking portions258, 253. One of the diametrical linking portions 258 has a wider shapethan the other, and through its interior passes a connecting hole 248 bywhich the axial recess 246 and the lower central recess 242 communicatewith one another. The annular recess 260 is formed with a depthdimension extending down to the bottom of the annular groove 256,whereby the bottom portion of the annular groove 256, excluding thelocations where the diametrical linking portions 258, 258 are formed,opens into the annular recess 260.

In the peripheral wall of the small-diameter recess 252 is bored acommunicating window 262 that extends over a predetermined length in thecircumferential direction. In this embodiment in particular, a pair ofcommunicating windows 262 of slot shape extending over a distanceslightly less than halfway around the circumference are formed spacedapart in the circumferential direction. With this arrangement, thesmall-diameter recess 252 communicates with the annular recess 260through the pair of communicating windows 262, 262. With the dividerblock 238 securely mated with the second mount fitting 214, the annularrecess 260 opens facing the rubber diaphragm 230, whereby thecommunicating windows 262 in the divider block 233 and thesmall-diameter recess 252 and annular recess 260 that communicate withone another through the communicating windows 262 constitute part of theequilibrium chamber 236.

A movable member 264 fmnctioning as a movable partition member isinstalled into the large-diameter recess portion 254. From the top ofthe movable member 264, a cover plate fitting 266 is assembledoverlapping the upper face of the divider block 238.

As illustrated in the single component diagrams in FIGS. 16 and 17, themovable member 264 has a circular, generally thin plate shape, and isformed by a rubber elastic body. The movable member 264 is securelymated with the large-diameter recess portion 254 of the divider block238, whereby the opening of the upper central recess 240 is providedwith fluid-tight closure by the movable member 264, thus forming thepressure receiving chamber 234 above the movable member 264 on the onehand, while forming the equilibrium chamber 236 below the movable member264.

The movable member 264, in a portion thereof situated generally on theinner peripheral edge of the stepped face 250 of the divider block 238,has an integrally formed annular elastic projection 268 that extendscontinuously or discontinuously in the circumferential direction. Atseveral locations on the circumference of the elastic projection 268(four locations in this embodiment) are integrally formed contactsupport portions 270 of generally plateau shape that project appreciablyfrom the upper and lower faces. In this embodiment, the distaledge-to-edge dimension of the elastic projections 268, 268 to the upperand lower sides of the movable member 264 is designed to be slightlysmaller than the axial dimension of the outer peripheral edge of themovable member 264, and the distal edge-to-edge dimension of the contactsupport portions 270, 270 on the upper and lower sides is designed to begenerally the same as the axial dimension of the outer peripheral edgeof the movable member 264.

A rigid constriction plate 272 consisting of metal or synthetic resin isembedded in the center portion of the movable member 264. As shown inFIG. 18, this constriction plate 272 is of generally shallow dish shapewhose center portion is slightly recessed, and while thin, providesimproved deformation rigidity. The constriction plate 272 has an outsidediameter dimension larger than the inside diameter dimension of theupper central recess 240 of the divider block 238, with the outerperipheral edge of the constriction plate 272 extending out to thestepped face 250.

A notch 274 is formed at each of several locations on the outerperipheral edge of the constriction plate 272 corresponding to the upperand lower contact support portions 270, 270, providing clearance at thelocations of the contact support portions 270, 270 when the constrictionplate 272 is covered by the movable member 264. The center of theconstriction plate 272 is perforated by circular hole 276 and covered bythe rubber material making up the movable member 264. Forming thiscircular hole 276 affords good distribution of rubber material onto bothfaces of the constriction plate 272, and also improves bond strength ofthe rubber to the constriction plate 272. Additionally, by adjusting thesize of the circular hole 276 and the thickness dimension of the rubberfilm closing off the circular hole 276, it is possible to appropriatelyadjust the elastic deformation characteristics of the movable member264. It is not absolutely necessary to form the circular hole 276,however.

In the portion situated between the elastic projection 268 and the outerperipheral edge in the movable member 264 is formed a thin peripheralmovable rubber film portion 278 of an annular plate shape extending inthe circumferential direction with predetermined width. This peripheralmovable rubber film portion 78 is situated on the annular groove 256formed in the stepped face 250 of the divider block 238.

As shown in FIG. 19, the cover plate fitting 266 has the overall form ofa thin, generally disk shaped member having a slight stepped portion 280formed in the diametrically medial portion, and a center portionprojecting downward with respect to the outer peripheral edge portion.The cover plate fitting 66 is superposed onto the upper face of thedivider block 238, and the stepped portion 280 is fitted into theopening of the upper central recess 240 of the divider block 238 toattach it positioned in the diametrical direction.

A round center through-hole 282 is formed in the center portion of thecover plate fitting 266, and around this center through-hole 282 areformed a number of outer peripheral through-holes 284 that extend apredetermined width in the circumferential direction. When the coverplate fitting 266 is installed on the divider block 238, a centermovable plate portion 286 of the movable member 264 reinforced by theconstriction plate 272 faces the pressure receiving chamber 234 throughthe center through-hole 282, and the peripheral movable rubber filmportion 278 faces the pressure receiving chamber 234 through the outerperipheral through-holes 284. The peripheral movable rubber film portion278 faces the equilibrium chamber 236 through the annular groove 256 ofthe divider block 23B.

A notched window 288 is provided at single circumferential location onthe outer peripheral edge of the cover plate fitting 266, this notchedwindow 288 being situated aligned with the upper opening shared by thecircumferential groove 244 and the axial groove 246 provided to thedivider block 238. In order to position the notched window 288 andgrooves 244, 246 so as to be aligned with one another, a positioningprojection 290 is disposed projecting from an appropriate location onthe circumference of the upper and face of the divider block 238, and apositioning hole 292 is formed at a corresponding location on the coverplate fitting 266, with positioning in the circumferential directionbeing realized through the mating action of the positioning projection290 and the positioning hole 292.

With the movable member 264 and the cover plate fitting 266 attached tothe divider block 238 in the above manner, as shown in enlarged view inFIG. 20, the contact support portions 270 of the movable member 264 aredisposed with the distal end faces thereof contacting the stepped face250 of the divider block 238 or the lower face of the cover platefitting 266, and appropriately compressed where necessary. The outerperipheral edge of the movable member 264 constitutes an elastic matingportion 294 of large axial dimension; when attached to the divider block238, the elastic mating portion 294 is disposed between the stepped face250 of the divider block 238 and the cover plate fitting 266, whilebeing compressively deformed in the direction of proximity of thedivider block 238 and the cover plate fitting 266. With thisarrangement, fluid-tight closure is provided to the opening of the uppercentral recess 240 in the divider block 238.

As shown in enlarged view in FIG. 21, the elastic projection 268 ispositioned across a slight gap from the stepped face 250 of the dividerblock 238 or the lower face of the cover plate fitting 266. When apressure fluctuation of the pressure receiving chamber 234 is exertedagainst the movable member 264, the movable member 264 undergoesdisplacement and deformation on the basis of the pressure differencebetween the pressure receiving chamber 234 and the equilibrium chamber236 exerted across the upper and lower faces of the movable member 264.In this embodiment, the elastic projection 268 functions as an elasticcontact projection and is brought into contact against a displacementrestricting member in the form of the cover plate fitting 266, therebyproviding displacement limiting member for cushion-wise limitation of anextent of displacement of the center movable plate portion 286.

With this arrangement, the deformation of the center movable plateportion 286 of the movable member 264 is limited by the constrictionplate 272 embedded therein. Thus, the displacement will be occurredprincipally on the basis of elastic deformation of the contact supportportions 270, 270. The peripheral movable rubber film portion 278, onthe other hand, is thin and readily undergoes elastic deformation on thebasis of a pressure differential between the pressure receiving chamber234 communicating through the peripheral through-holes 284 of the coverplate fitting 266 and the equilibrium chamber 236 communicating throughthe annular groove 256 of the divider block 238, so that displacement isproduced due to deformation.

The openings of the circumferential groove 244 and the axial groove 246formed on the outer peripheral face of the divider block 238 are eachprovided with fluid-tight closure by the second mount fitting 214. Byproviding closure to the circumferential groove 244, there is formed afirst orifice passage 296 connecting the pressure receiving chamber 234and the equilibrium chamber 236 to one another, this passage beingnormally in the open state. By providing closure to the axial groove246, there is formed a second orifice passage 298 that passes from theconnecting hole 248 through the lower central recess 242 of the dividerblock 238 and opens into the equilibrium chamber 236, connecting theequilibrium chamber 236 to the pressure receiving chamber 234.

This second orifice passage 298 is formed with approximately the samepassage cross sectional area as the first orifice passage 296, andshorter passage length. By means of this design, the second orificepassage 298 is tuned to a higher frequency range than the first orificepassage 296. Specifically, the resonance frequency of fluid caused toflow through the first orifice passage 296 is tuned so as to exhibit, onthe basis of resonance action of the fluid, high attenuationcharacteristics against engine shake or other low-frequency,small-amplitude vibration on the order of ±0.1 mm and 10 Hz, and engineshake or other low-frequency, large-amplitude vibration on the order of±1.0 mm and 10 Hz, for example. The resonance frequency of fluid causedto flow through the second orifice passage 298 is tuned so as toexhibit, on the basis of resonance action of the fluid, high attenuationcharacteristics against idling vibration or other medium-frequency,medium-amplitude vibration on the order of ±0.1-0.25 mm and 20-40 Hz,for example. The characteristic frequency of the movable member 264,based on displacement and deformation of the movable member 264, istuned so that the movable member 264 is effectively made to produceresonance phenomenon against driving booming noise or otherhigh-frequency, very small amplitude vibration on the order of ±0.1-0.02mm and 60-120 Hz, for example.

To the mount body resulting from attachment of the divider member 228and the rubber diaphragm 230 to the integrally vulcanization moldedcomponent of the rubber elastic body 216 having the first mount fitting212 and the second mount fitting 214, there is additionally attached abracket 218. The bracket 218 has a large-diameter, deep-bottomedgenerally bottomed cylindrical shape overall, and is fastened fittingonto the exterior of the second mount fitting 214. The bracket 218 isthen secured press-fit into a cylindrical fastener fitting 300 having alarge-diameter, generally cylindrical shape. The cylindrical fastenerfitting 300 being bolted to the vehicle body, whereby the second mountfitting 314 is mounted onto the vehicle body by means of the bracket318.

The bracket 318 is sufficiently deep-bottomed relative to the secondmount fitting 314, so that with the second mount fitting 314 scouredfitting therein, there is formed an internal space 302 of sufficientsize located in the lower portion of the bracket 318. By means of thisinternal space 302 the rubber diaphragm 230 is permitted to undergobulging deformation to a sufficiently large extent.

Also disposed in the lower portion of the bracket 218 is a pneumaticactuator 304. This pneumatic actuator 304 utilizes the floor of thebracket 218 as a base housing 306, and is attached to the base housing306 so that an output member 308 serving as the valve member ispositioned inside the bracket 218.

The output member 308 comprises a divider rubber 310 of generally hatshape overall, with the center portion of the divider rubber 310constituting an output portion 312 of inverted cup shape, and with theouter peripheral portion constituting a tapered, flange-shaped elasticperipheral wall portion 314 that flares downward on the diagonal fromthe rim at the lower end of the output portion 312. The output portion312 has embedded therein a rigid reinforcing member 316 formed of metalor synthetic resin, while an annular press-fitting fixture 318 isvulcanization bonded to the outer peripheral edge of the peripheral wallportion 314.

By press fitting the press-fitting fixture 318 against the bottomperipheral wall of the bracket 218, the outer peripheral edge of thedivider rubber 310 is placed in fluid-tight contact against the bottomface of the base housing 306 formed by the bracket 218. By means of thisdesign, the opening of the output member 308 is provided with closure bythe bottom wall of the base housing 306 to constitute the pneumaticactuator 304 having a pressure regulating air chamber 320 formed inside.

In this embodiment, a compressed coil spring 322 is attachedaccommodated within the pressure regulating air chamber 320, so thaturging force is normally exerted in the direction pushing the outputportion 312 and the base housing 306 apart from one another. An air port324 passes through the center of the floor of the base housing 306.Pressure in the pressure regulating air chamber 320 can be controlledfrom the outside through this air port 324.

Specifically, with the engine mount 210 installed, an external airpressure line 326 is connected to the air port 324, and a switch valve328 is connected via the air pressure line 326. In accordance withswitching operation of the switch valve 328, the pressure regulating airchamber 320 is selectively connected to the atmosphere or to a negativepressure source 330.

With the pressure regulating air chamber 320 connected to theatmosphere, by mean of the action of the elastic behavior of the elasticperipheral wall portion 314 and the elastic behavior of the compressedcoil spring 322 on the output portion 312, the output portion 312 iscaused to project resiliently upward, urging the rubber diaphragm 230upward and holding it pressed against the center lower face of thedivider block 238 in the divider member 228. Since the contour of theoutput portion 312 is larger than the opening diameter of the lowercentral recess 242 formed on the center lower face of the divider block238, the center portion of the rubber diaphragm 230 is pushed againstthe opening of the lower central recess 242 and provides substantiallyfluid-tight closure thereto, whereby the second orifice passage 298which opens into the equilibrium chamber 236 through the lower centralrecess 242 is closed off.

On the other hand, with the pressure regulating air chamber 320connected to the negative pressure source 330, on the basis of thepressure differential between outside atmospheric pressure and thenegative pressure exerted inside the pressure regulating air chamber320, the output portion 312 is drawn into the pressure regulating airchamber 320 in opposition to the elastic behavior of the elasticperipheral wall portion 314 and the elastic behavior of the compressedcoil spring 322, causing it to become displaced axially downward. Thus,the rubber diaphragm 230 separates from the opening of the lower centralrecess 242, opening the second orifice passage 298 and placing it in theopen state.

In this embodiment, the switch valve 328 is switched by the controller332 according to whether the vehicle is driving or at a stop. That is,during driving, the pressure regulating air chamber 320 is connected tothe atmosphere, whereas when at a stop, the pressure regulating airchamber 320 is connected to the negative pressure source 330. Thecontroller 332 is advantageously constituted, for example, so as tooutput a drive control signal to an electromagnetic solenoidconstituting the switch valve 328, by means of an acceleration sensor orthe like.

Accordingly, in the engine mount 210 of the construction describedabove, low frequency, large amplitude vibration input when driving overa speed bump or the like is not attended by consequent liquid pressureabsorption through displacement and deformation of the movable member264 comprising the center movable plate portion 286 and the peripheralmovable rubber film portion 278, so that effective pressure fluctuationis produced in the pressure receiving chamber 234. With thisarrangement, relative pressure fluctuations between the pressurereceiving chamber 234 and the equilibrium chamber 236 are effectivelyproduced. Thus, as long as the second orifice passage 298 is maintainedin the closed state by the output member 308, fluid flow volume throughthe first orifice passage 296 is advantageously assured, a high level ofattenuating effect based on flow action, e.g. resonance action, of thefluid induced to flow through the first orifice passage 296 isexhibited, and excellent vibration damping ability is achieved.

In response to low frequency, small-amplitude vibration input duringnormal driving, as with the low frequency, large-amplitude vibrationdescribed earlier, as long as the second orifice passage 298 ismaintained in the closed state by the output member 308, fluid flowvolume through the first orifice passage 296 is advantageously assured.Thus, a high level of attenuating effect based on flow action, e.g.resonance action, of the fluid induced to flow through the first orificepassage 296 is exhibited, and excellent vibration damping ability isachieved. While pressure absorption of the pressure receiving chamber234 by the movable member 264 is a concern, in this embodiment, sincefluid-tightness at the outer peripheral side of the center movable plateportion 286 is assured by the peripheral movable rubber film portion278, and since the extent of deformation of the movable member 264 issuppressed by the rigidity of the center movable plate portion 286,whereby adequate pressure fluctuations are created in the pressurereceiving chamber 234.

Since pressure fluctuations of the pressure receiving chamber 234 inresponse to high-frequency, very small amplitude vibration input duringdriving are extremely small, the pressure fluctuations of the pressurereceiving chamber 234 are effectively absorbed and lessened by means ofdisplacement and deformation of the movable member 264. In particular,since the center movable plate portion 286 of the movable member 264 canbe formed in the center portion to advantageously assure effectivesurface area, whereas the outer peripheral edge portion thereof isconstituted as fluid-tightly supported, readily deformable peripheralmovable rubber film portion 278, following displacement in response tohigh frequency pressure fluctuations in the pressure receiving chamber234 can advantageously be achieved, and pressure fluctuations in thepressure receiving chamber 234 can be suppressed.

Additionally, since the characteristic frequency of the movable member264 is tuned to the high frequency range of vibration to be damped, whenhigh frequency vibration is input, the movable member 264 moreadvantageously undergoes following displacement on the basis ofresonance action. Thus, when high frequency vibration is input, evenwith the first and second orifice passages 296, 298 in the substantiallyclosed state, sharp pressure fluctuations in the pressure receivingchamber 234 can be avoided by means of the movable member 264, andexcellent vibration damping action may be achieved by means of effectivevibration isolating action based on low dynamic spring characteristics.

Further, in response to medium-frequency, medium-amplitude vibrationinput with the vehicle at a stop, while pressure absorption of thepressure receiving chamber 234 by the movable member 264 is a concern,in this embodiment, since the extent of deformation of the movablemember 264 is suppressed on the basis of the rigid center movable plateportion 286 disposed in the center portion of the movable member 264,and since the peripheral movable rubber film portion 278 is disposed tothe outside of the center movable plate portion 286, ensuring that thepressure receiving chamber 234 is fluid-tight, pressure leakage from thepressure receiving chamber 234 to the equilibrium chamber 236 areavoided, so that adequate pressure fluctuations are created in thepressure receiving chamber 234. Thus, by means of operation of thepneumatic actuator 304 to place the second orifice passage 298 in theopen state, a sufficient level of fluid flow through the second orificepassage 298 is adequate assured, whereby high damping effect based onflow action, e.g. resonance action, of the fluid induced to flow throughthe second orifice passage 298 is achieved, and excellent vibrationdamping ability is exhibited. Additionally, with the second orificepassage 298 in the open state, the first orifice passage 296 is in theopen state as well, but since medium-frequency input vibration of afrequency range above of the tuning frequency of the first orificepassage 296 will be countered by the first orifice passage 296 becomingsubstantially closed due to antiresonant action of fluid through thefirst orifice passage 296, the level of fluid flow through the secondorifice passage 298 is effectively assured.

Accordingly, in the engine mount 210 of this embodiment, the firstorifice passage 296, the second orifice passage 298, and the movablemember 264 each function efficiently in response to the frequency andamplitude of vibration to be damped, whereby effective vibration dampingaction is exhibited against vibration of multiple, wide frequencyranges.

In this embodiment, the movable member 264 that comprises a centermovable plate portion 286 and a peripheral movable rubber film portion278 is employed. In the event where suppression of liquid pressureabsorption of the pressure receiving chamber 234 by the movable member264 is required to thereby effectively producing pressure fluctuationsin the pressure receiving chamber 234, e.g. during input oflow-frequency, small-amplitude vibration or medium-frequency,medium-amplitude vibration as described previously, since the fact thatthe extent of deformation of the movable member 264 is suppressed by therigid center movable plate portion 268 formed in the center of themovable member 264, and since fluid-tightness on the outer peripheralside of the center movable plate portion 286 is assured by theperipheral movable rubber film portion 278, effective pressurefluctuations are produced in the pressure receiving chamber 234. Thus,since adequate fluid flow levels through the first orifice passage 296or second orifice passage 298 are assured, by selectively switching thesecond orifice passage 298 between the open state and the closed state,vibration damping effect based on fluid flow action through the orificepassages 296, 298 can be advantageously achieved. As will be understoodfrom the foregoing description, an intermediate equilibrium chamber isformed by a portion 236′ formed integrally with the equilibrium chamber236 in this embodiment.

As a result, even in the absence of a special construction as taught infor example JP-A-2002-5225 whereby an air chamber is formed on theopposite side of the movable member from the pressure receiving chamber,and air pressure from the outside (either negative pressure or positivepressure) is exerted causing the movable member to undergo constrictingdeformation, the desired vibration damping effect can nevertheless beachieved on the basis of suppressing the extent of deformation anddisplacement by means of the construction of the movable member 264 sothat pressure fluctuations are effectively produced in the pressurereceiving chamber 234. Thus, the desired vibration damping effect can beachieved consistently, by memos of ensuring a high degree of freedom indesign of placement space etc. of the first orifice passage 296, thesecond orifice passage 298, and the movable member 264 in associationwith the simpler internal structure including the divider member 228.

Additionally, since as compared to the vibration damping mount ofconventional construction including that of JP-A-2002-5225 cited above,there is no need to form in the divider member an air chamber or airpassage for exerting air pressure on the air chamber from the outsidesor to provide an air port in the second mount fitting, manufacture iseasier, and good fluid-tightness of the pressure receiving chamber 234and the equilibrium chamber 236 may be assured.

In this embodiment, provided that the level of fluid-tightness requiredof the pressure receiving chamber 234 is assured, even in the event thatthere is some leakage of fluid from the pressure receiving chamber 234to the outside of the movable member 264, since the opposite side of themovable member 264 from the pressure receiving chamber 234 is theequilibrium chamber 236, there is no problem of fluid leaking out intoan unsealed zone, whereby quality performance may be improved.

Further, in this embodiment, by forming the elastic projection 268 andthe contact support portions 279 as elastic contact projections on themovable member 264, the extent of displacement of the movable member 264can be limited, thus more effectively suppressing pressure absorption bythe movable member 264 during input of low-frequency, small-amplitudevibration.

In the engine mount 210 of this embodiment, since the constriction plate272 is securely embedded in the center movable plate portion 286 of themovable member 264, it is possible to more reliably suppress absorptionof pressure fluctuations of the pressure receiving chamber 234 duringlow- to medium-frequency vibration input due to unwanted deformation ofthe center movable plate portion 286, whereby vibration damping actionbased on flow action in the first orifice passage 296 and the secondorifice passage 298 is effectively exhibited.

While the present invention has been described in detail in itspresently preferred embodiments, for illustrative purpose only, it is tobe understood that the invention is by no means limited to the detailsof the illustrated embodiments, but may be otherwise embodied. It isalso to be understood that the present invention may be embodied withvarious changes, modifications and improvements which may occur to thoseskilled in the art, without departing from the spirit and scope of theinvention.

For example, in the second embodiment, it is possible to modifyappropriately the shape, size, and construction of the small-diameterrecess portion constituting part of the equilibrium chamber 236, thecommunicating window 262, and the annular recess 260 to make part of theequilibrium chamber 236 function as a fluid passage, as well as to tunethe resonance frequency of the fluid induced to flow through the flowpassage to a high-frequency, very small-amplitude vibration frequencyrange on the order of ±0.03 and 80 Hz, for example.

Also, whereas in the second embodiment hereinabove, the center movableplate portion 286 is reinforced by embedding a rigid constriction plate272, the constriction plate 272 could be dispensed with. Specifically,by making the movable member 264 thicker as necessary to impartsufficient rigidity, it becomes possible to exhibit functionality as thecenter movable plate portion 256, even without being reinforced by theconstriction plate 272.

Also, whereas in the embodiment hereinabove a compressed coil spring 322is used as the urging means for pushing against the opening of the lowercentral recess 242, the urging means is not limited to that taught inthe embodiment. Specifically, it would be possible to instead simplyutilize the elastic behavior of the divider rubber 310 to maintain astate of contact, or to use a plate spring or the like instead of acompressed coil spring 322.

The shape, size, and construction of the center movable plate portion286 and the peripheral movable rubber film portion 278 in the movablemember 264, as well as the placement location of the movable member 64with respect to the divider member 228, are not limited to those taughtherein by way of example, and may be modified appropriately depending onthe required vibration damping characteristics, producibility, and otherconsiderations.

The shape, size, construction, and number of the orifice passages formedin the divider member 228 are not limited to the first and secondorifice passages taught in the second embodiment hereinabove, withappropriate modifications thereto being apparent to the skilledpractitioner of the art.

Further, whereas the embodiment hereinabove describes application of theinvention in an automotive engine mount by way of a specific example,the invention could of course be implemented advantageously innon-automotive engine mounts as well.

1. A pneumatically switchable type fluid-filled engine mount,comprising: a first mounting member attachable to one of a power unitside member and a vehicle body side member; a second mounting memberattachable to an other of the power unit side member and the vehiclebody side member; a rubber elastic body elastically connecting the firstmounting member and the second mounting member; a pressure receivingchamber partially defined by the rubber elastic body, filled with anon-compressible fluid, and subjected to input of vibration; anequilibrium chamber partially defined by a flexible layer for readilypermitting change in volume thereof, and filled with thenon-compressible fluid; a first orifice passage for fluid communicationbetween the pressure receiving chamber and the equilibrium chamber,tuned to a low frequency range generally corresponding to engine shake;a second orifice passage for fluid communication between the pressurereceiving chamber and the equilibrium chamber, tuned to a mediumfrequency range generally corresponding to idling vibration; a valvemember for opening/closing the second orifice passage; a pneumaticactuator operated by air pressure from the outside, for driving thevalve member; it movable partition member whose center portionconstitutes a rigid center movable plate portion and whose outerperipheral portion constitutes a readily deformable outer peripheralrubber film portion, disposed so that an outer peripheral edge of theouter peripheral rubber film portion is supported fluid-tightly by thesecond mount portion, permitting displacement and deformation in thecenter movable plate portion and the outer peripheral rubber filmportion, the movable partition member defining another part of thepressure receiving chamber; and an intermediate equilibrium chamberformed on an opposite side of the movable partition member from thepressure receiving chamber with the movable partition member interposedbetween the intermediate equilibrium chamber and the pressure receivingchamber.
 2. A pneumatically switchable type fluid-filled engine mountaccording to claim 1, wherein the intermediate equilibrium chambercomprises an air chamber open to an atmosphere.
 3. A pneumaticallyswitchable type fluid-filled engine mount according to claim 2, whereinthe first mounting member is disposed at and spaced apart from a firstaxial open end of the second mounting member of cylindrical shape, withthe first mounting member and the second mounting member being connectedby the rubber elastic body to thereby fluid-tightly close the firstaxial open end of the second mounting member, and an other open end ofthe second mounting member is covered fluid-tightly by the flexiblelayer, while a partition member is disposed between the rubber elasticbody and the flexible layer and supported by the second mounting memberso that the pressure receiving chamber and equilibrium chamber areformed to either side of the partition member; wherein the movablepartition member is disposed in the partition member on a side facingthe pressure receiving chamber, and the air chamber is formed on a backside of the movable partition member remote from the pressure receivingchamber in the partition member, while an air passage is formedextending from the air chamber to an outer circumferential surface ofthe second mounting member through the partition member and the secondmounting member, wherein the first orifice passage is formed so as toextend along an outer peripheral portion of the partition member in ancircumferential direction, and the second orifice passage is formed soas to extend with a predetermined length in an axial direction at anouter peripheral side of the movable partition member in the partitionmember, and extend radially inwardly through an inner portion of thepartition member, the second orifice passage being open to thepressure-receiving chamber through a first opening formed at an outerperipheral side of the movable partition member in the partition memberand being open to the equilibrium chamber through a second openingformed at a central portion of the partition member; and wherein theflexible layer is superimposed onto the second opening of the secondorifice passage to constitute the valve member, the valve member beingdriven by the actuator to carry out opening/closing control of thesecond orifice passage by alternately opening and closing the secondopening of the second orifice passage, and a second opening peripheralportion that extends outwardly in an axis-perpendicular direction fromthe second opening of the second orifice passage has a dilated shape ofgradually increasing width dimension in the circumferential directiongoing outwardly in the axis-perpendicular direction.
 4. A pneumaticallyswitchable type fluid-filled engine mount according to claim 1, whereinthe intermediate equilibrium chamber is formed integrally with theequilibrium chamber so that the center movable plate portion and theperipheral movable rubber film portion undergo displacement anddeformation on the basis of a pressure difference between the pressurereceiving chamber formed on one side thereof and the equilibrium chamberformed on an other side thereof so as to absorb, by means of thedisplacement and deformation, pressure fluctuation in the pressurereceiving chamber during input of vibration in a high frequency bandcorresponding to drive booming noise.
 5. A pneumatically switchable typefluid-filled engine mount according to claim 4, wherein a portion of theequilibrium chamber is constricted to form a fluid passage, and thedisplacement and deformation of the movable partition member based on apressure difference between the pressure receiving chamber and theequilibrium chamber, exerted on either face of the movable partitionmember permits a substantial fluid flow through the fluid passage.
 6. Apneumatically switchable type fluid-filled engine mount according toclaim 4, wherein the first mounting member is disposed at and spacedapart from a first axial open end of the second mounting member ofcylindrical shape, with the first mounting member and the secondmounting member being connected by the rubber elastic body to therebyfluid-tightly close the first axial open end of the second mountingmember, and an other open end of the second mounting member is coveredfluid-tightly by the flexible layer, while a partition member isdisposed between the rubber elastic body and the flexible layer andsupported by the second mounting member so that the pressure receivingchamber and equilibrium chamber are formed to either side of thepartition member; wherein the movable partition member is displaceablyand deformably disposed so as to extend at a generally right angle tothe direction of opposition of the pressure receiving chamber and theequilibrium chamber in the partition wall member; and wherein the firstorifice passage is formed so as to extend along an outer peripheralportion of the partition member in an circumferential direction, and thesecond orifice passage is formed so as to extend with a predeterminedlength in an axial direction at an outer peripheral side of the movablepartition member in the partition member, and extend radially inwardlythrough an inner portion of the partition member, the second orificepassage being open to the pressure-receiving chamber through a firstopening formed at an outer peripheral side of the movable partitionmember in the partition member and being open to the equilibrium chamberthrough a second opening formed at a central portion of the partitionmember; and wherein the flexible layer is superimposed onto the secondopening of the second orifice passage to constitute the valve member,the valve member being driven by the actuator to carry outopening/closing control of the second, orifice passage by alternatelyopening and closing the second opening of the second orifice passage. 7.A pneumatically switchable type fluid-filled engine mount according toclaim 1, wherein an elastic contact projection is formed projecting outfrom an outer peripheral edge portion of the center movable plateportion in the movable partition member, the elastic contact projactionbeing positioned in contact against the second mounting member or adisplacement restricting member supported by the second mounting member,thereby providing displacement limiting member, for cushion-wiselimitation of an extent of displacement of the center movable plateportion.
 8. A pneumatically switchable type fluid-filled engine mountaccording to claim 1, wherein the pneumatic actuator is operable suchthat during driving of an automobile, the valve member is driven bygenerally atmospheric pressure applied from an outside whereby thesecond orifice passage assumes a closed state thereof, and when theautomobile is at a stop the valve member is driven by negative pressureapplied from the outside whereby the second orifice passage assumes anopen state.
 9. A pneumatically switchable type fluid-filled engine mountaccording to claim 1, wherein a rigid constriction plate is disposed inthe center movable plate portion of the movable partition member, withthe outer peripheral rubber film portion being bonded to theconstriction plate.
 10. A pneumatically switchable type fluid-filledengine mount according to claim 1, wherein displacement and deformationcharacteristics of the movable partition member are designed so that, inthe event that input vibration applied across the first mounting memberand the second mounting member is very small amplitude vibration of±0.05 mm or less, pressure fluctuations produced in the pressurereceiving chamber can be substantially absorbed; whereas in the eventthat input vibration applied across the first mounting member and thesecond mounting member is small amplitude vibration of about ±0.1 mm orlarge amplitude vibration of ±1.0 mm or more, pressure fluctuationsproduced in the pressure receiving chamber cannot be substantiallyabsorbed.